Goto skipping declarations

[Jonathan M Davis]

On Friday, May 3, 2024 1:15:16 PM MDT Ben Jones via Digitalmars-d-learn wrote:
> In general, you can't skip a declaration with goto, but it seems
> to be allowed if the declaration you're skipping is labelled...
> Is that expected or an accepts invalid bug?
>
> https://godbolt.org/z/4qx8Pf6G7
>
> ```d
> void f1(){ //fails with error about skipping a declaration
>      int x;
>      goto Label;
>      int y;
>      Label:
>      int z;
> }
>
> void f2(){ //compiles fine
>      int x;
>      goto Label;
>      Dummy:
>      int y;
>      Label:
>      int z;
> }
> ```

It has to be a bug, and taking it a step further shows that. If you print
out y, you'll get a seemingly random number. E.G. On the first run, I got

554440803

and on the second I got

549310547

Presumably, it's a garbage value from whatever happened to be on the stack.

I'm quite sure that the spec doesn't have anything about being allowed to
skip a declaration just because it has a label on it (honestly, if we _did_
want that to be the case, the spec would probably be missing it, since it
tends to fall on the side of having too few details rather than too many),
but even if it did, the code is clearly doing something that should not be
happening with initialization without explicitly using = void. So,
_something_ here would nee to be fixed.

In any case, I expect that the compiler is just going dumb here because of
the label for some reason, and one or more of the checks that it's supposed
to be doing is being missed.

- Jonathan M Davis